"Data Integrity Violation Error" when updating users through a REST API Call

Question 

Why do I get the following error when I try to update a user using the xMatters REST API? 

Could not create user. Returned error: Data Integrity Violation Error.

Environment

All versions of xMatters 

Answer

Text fields are limited to a maximum of 100 characters. You’re receiving this error because one of the text fields in your User Upload file is too long.